1. Field of the Invention
The present invention relates to electrical connectors, more particularly, to electrical connectors for joining power regulators to a voltage bus. In particular, the present invention relates to a means of providing a bus bar connection with dual levels of resistance.
2. Background of the Invention
Power regulators for large computer systems such as the IBM ES/3090 supply power at low voltage (e.g., 1.4 V, 2.1 V, 3.6 V) and high current (on the order of several hundred amps), to the computer system. Typically, solid conductor bus bars connect this type of power supply to the voltage bus of the computer system. The solid bus bars are necessary to carry the high current flow.
Large computer systems supporting a department or corporation must be extremely reliable and have high availability. One way of increasing reliability is to include redundant components so that component function can continue even if one of the components fails. A particular computer system may have several power supplies and, by adding at least one additional spare power supply, can be configured to operate when one of the power supplies fails.
Replacement of a power supply while a computer system is operating introduces certain problems. In particular, connection of a replacement power supply to an operating voltage bus can lead to voltage transients on the bus resulting in irrecoverable logic errors. Transients occur because the output filter capacitors of the replacement power regulator are initially uncharged and, upon connection to an operating voltage bus, appear as a short circuit to the bus causing a momentary voltage drop on the bus while the capacitors are charged.
The prior art suggests several solutions to the problem of charging the output filter capacitors. One approach is to add isolation diodes to the power regulator output to prevent current flow from the voltage bus. Diodes operating in a low voltage, high current circuit such as described herein would operate at a very low level of efficiency and would generate considerable heat. Neither of these results is desirable in a power regulator for computer systems.
A second prior art solution is to provide a method of pre-charging the capacitors before connecting the power regulator to the voltage bus. This is described, for example, in IBM Technical Disclosure Bulletin Volume 27, No. 12, pp. 7239-7241. The disadvantage of this approach is that technician training and monitoring are required to ensure that the connection of the AC input power, the charging of the capacitors, and the final connection to the voltage bus occur in the proper sequence. Failure to follow the correct sequence could result in the undesirable voltage transients discussed above. A requirement for a two-step connection process increases the complexity and reduces the reliability of the overall system.